Chrome alone is 65% of all browsers. So Chrome dropping RSS support already addresses an overwhelming majority of all potential readers.

<https://gs.statcounter.com/browser-market-share>

Google's interests are pretty evident and self-serving: RSS short-circuits both the browser (you can use an RSS reader) and Google's search engine. Both directly reduce advertising exposure.

Firefox killed default RSS features in 2018 "because they're hardly used and would take too much effort to modernise":

<https://www.zdnet.com/article/end-nears-for-rss-firefox-64-t...>

Browser extensions can still be used to read RSS feeds.

No one used it. Outside of tech circles, no one even knew what RSS was.

Sites like Reddit also killed it. People would rather subscribe to topics (subreddits) than individual blogs.